Dry chemical fire extinguishers



United States Patent DRY CHEMICAL FIRE EXTINGUISHERS William R. Warnockand James A. Lindlof, Menominee,

M1ch., and Rodney L. Hemminger, Marinette, Wis,

assignors to Ansul Chemical Company, Marinette, Wis., a corporation ofWisconsin N Drawing. Filed Feb. 6, 1959, Ser. No. 791,522

4 Claims. (Cl. 169-31) This invention relates to charges for drychemical fire extinguishers and more particularly to stored pressuretypeextinguishers.

In stored pressure extinguishers the charge usually consists of anextinguishing agent and an expellant gas and these should be present inan appropriate weight ratio for satisfactory operation. If theextinguisher cavity is filled full with dry chemical powder, forexample, addition of the necessary amount of expellant gas will resultin a high pressure and consequently, a heavy and expensive shell isneeded to contain it.

If it is desired to use a lighter weight and less expensive shell, theamount of dry chemical can be reduced to allow a greater volume for theexpellant gas, thereby reducing its pressure. However, this obviouslyreduces the amount of extinguishing agent available for discharge from agiven size extinguisher. It is also desirable that there be someconvenient and reliable method of determining the state of readiness foruse of the extinguisher.

Extinguishers currently available will usually discharge satisfactorilyif they are handled properly. Frequently a pressure gauge is relied uponto indicate the presence of sutlicient gas for effective discharge ofthe extinguishing agent. Gauges have been known to give inaccuratereadings by virtue of damage to the mechanism, plugging, etc. However,if the quantity of expellant gas is large in proportion to the grossweight of the extinguisher, readiness for use can be ascertained bydetermining the weight of the extinguisher.

Therefore, one of the objects of this invention is to provide anextinguisher in which a maximum proportion of the gross weight of theextinguisher consists of the dry chemical extinguishing agent.

It is also an object of this invention to provide a dry chemical fireextinguisher which will, without excessive pressures or reduction in theamount of dry chemical powder, contain such a large amount of expellantgas that a weighable amount of said gas can escape or leak from theextinguisher without impairment of the fire fighting capabilities of theextinguisher.

It is another object of this invention to provide an extinguisher whosesuitability for use can be reliably 5 ascertained by determining itsweight within reasonable limits.

=We have found that these objects can be accomplished by the addition ofa highly adsorptive material to the dry chemical extinguishing agent.This adsorptive material should have a high surface area per unit ofvolume which enables small amounts of it to adsorb enough of theexpellant gas so that when the extinguisher is fully charged, thepressure will be considerably below that usually expected; or statedanother way, a large quantity of gas can be charged without exceeding apreselected pressure, all

pressures referred to being gauge pressure measured at 70 F. Theinvention is illustrated by the following examples.

Example 1 An extinguisher shell of 72 cu. in. capacity was filled with1135 g. standard dry chemical fire-extinguishing powder and pressurizedwith carbon dioxide. Dry chemical fire-extinguishing powder consistsessentiallly of powdered sodium bicarbonate and additives to maintainthe powder in dry freeaflowing condition as disclosed in US.

Patents 1,793,420 and 2,631,977. For proper operation of thisextinguisher, 30 to 35 grams of CO are required by fire-extinguisherapproval agencies. When 19 grams of CO had been admitted, the pressurewas 200 psi, 30 grams of CO raised the pressure to 300 p.s.i. and 35grams to 350 p.s.i. Thus, a pressure between 300 and 350 psi. would berequired, and the extinguisher to withstand these pressures wouldnecessarily be expensive and heavy. When the extinguisher was filledwith dry chemical powder modified by the addition of 10 percent silicagel, 20 grams of CO were present at only p.s.i. and by the time thepressure stood at 200 psi, 38 grams had been admitted.

Because of ICC regulations, inspection codes, and so forth, it isdesirable to limit the pressure at 70 F. to 200 p.s.i. The presence ofthe adsorptive agent enables maximum amounts of .both extinguishingagent and expellant gas to be charged to the extinguisher withoutexceeding this limit.

The effectiveness of the adsorptive agent is further evident when it isrealized that the extinguisher with no powder in it at all containedonly 33 grams of CO at 200 p.s.i. The presence of the adsorptive agentmay also enhance the discharge characteristics of the dry chemicalpowder. In the extinguisher mentioned above 95 percent of the powder wasexpelled, percent being considered an acceptable value.

Other adsorbing agents are also suitable. In general, they should have ahigh surface area as determined by nitrogen adsorption or someequivalent method. It is preferred that the particle size of theadsorbing agent should be of the same order of magnitude as the drychemical agent, but wide variations are Permissible in this respect.Examples of other suitable adsorbents are activated charcoal, attapulgusclay, synthetic zeolites (molecular sieves), activated alumina, crackingcatalysts of the type used in petroleum refining containing silica andvarious proportions of alumina. We may also use the porous materialsdisclosed in Patent 2,866,760.

The expellant gases suitable for use in the present invention includecarbon dioxide, nitrous oxide, ethane, halogenated hydrocarbons,nitrogen, and air, including mixtures of the foregoing.

We have found that for best results the adsorbent should be as free aspossible of adsorbed water before addition to the dry chemical powderand should be protected from the atmosphere until charged to theextinguisher. In general, heating the adsorbent to 300400 F. for a fewhours accomplished adequate drying. It is preferred that the adsorbentbe mixed with the dry chemical powder but this is not essential for thesuccessful practice of this invention. Materials which do not have ahigh surface area are not satisfactory as adsorbents. For example, verysmall glass beads or talc cannot be used.

Example 2 The extinguisher of Example 1 was filled with a chargecomprising 85 percent dry chemical fire-extinguishing powder and 15percent of an adsorbing agent, silicaalumina micro spheres of the typeused as a catalyst in fluid bed petroleum cracking operations having 75percent silica and 25 percent alumina. The extinguisher was pressurizedwith CO to 200 p.s.i., 38 grams being admitted.

Other gases may also be used but some discretion should be exercised tomake sure the adsorbing agent will adsorb the chosen expellant.

Example 3 The fire extinguisher of Example 1 was filled with a chargecomprising percent standard dry chemical fireextinguishing agent and 10percent silica gel having a fine particle size. Nitrous oxide wascharged to 200 p.s.i., 37

3 grams being required. When the extinguisher was discharged, less than10 percent of the solids remained in the extinguisher.

When this empty extinguisher was filled to 200 p.s.i. with nitrousoxide, 31 grams were required. When it was filled with standardfire-extinguishing powder containing no adsorptive agent, only 19 gramsof nitrous oxide could be admitted at 200 p.s.i.

Our invention is equally effective when the expellant gas comprises morethan one chemical compound.

Example 4 A two-component expellant gas consisted of approximat-elyequal quantities of dichlorodlfluoromethane and carbon dioxide. Incharging the extinguisher, the procedure was to first fill withextinguishing agent, charge the dichlorodifiuoromethane to 38 p.s.i. andthen add CO to 190 p.s.i. (all at 70 F.).

When the extinguisher was charged with gas as above and no dry chemicalpowder, it held about 39 gram of expellant gas, but when filled firstwith sodium bicarbonate powder, the gas weight was reduced to only 23grams, much less than the desired 30-35 grams, although chargingpressures were the same.

When the extinguisher =was filled with a dry chemical extinguishingagent composed of 90 percent NaHCO and 10 percent attapulgus clay, wewere able to introduce 39 grams of expellant gas On fire tests with thelatter dry chemical, composition, well over 85 percent of the drychemical was effectively discharged.

Example 5 The procedure for Example 4 was repeated except thatmonochlorodifluoromethane was substituted for the halogenatedhydrocarbon. When the extinguisher was filled with a powdered drychemical extinguishing agent composed of 90 percent sodium bicarbonateand percent attapulgus clay and then pressurized to 40 p.s.i. with themonochlorodifluoromethane, and then to 190 p.s.i. with carbon dixiode,17 grams of monochlorodifluoromethane and 18 grams of CO were admittedmaking a total of 35 grams of expellant gas. On discharge tests, 94percent of the dry chemical was effectively expelled.

Example 6 The test extinguisher was filled with dry chemical composed of90 percent sodium bicarbonate and 10 percent silica gel and pressurizedto 50 p.s.i. with monochlorodifluoromethane and then to 200 p.s.i. withnitrogen. This procedure gave 36 grams of expellant, 27 grams ofmonochlorodifluoromethane plus 9 grams of nitrogen.

Example 7 A dry chemical fire-extinguishing powder was prepared whichconsisted of .10 percent finely divided attapulgus clay and 90 percentfinely divided sodium bicarbonate. 1135 grams of this powder were placedin a 72 cu. in. fire extinguisher shell and1-chlorodifluoro-2-chlorodifluoroethane was admitted to a pressure of 10p.s.i. and then CO was added to a pressure of 200 p.s.i. This proceduregave a total expellant charge of 32 grams, 7 grams of which were thesaid halogenated hydrocarbon. On discharge tests, 96 percent of theextinguished agent was expelled from the extinguisher.

As indicated in the above examples, the nature of the expellant gas canvary widely. However, the expellant gas should be non-reactive with theingredients in the dry chemical fire-extinguisher charge; for example ahighly acidic gas could not be used with a sodium bicarbonate basedfire-extinguishing agent. It is possible to use a combustible gas, suchas ethane, as an expellant, since the quantity of fuel added to the firein this manner is infinitesimal when compared to the quantity of fuelalready being consumed by the fire.

The adsorbent may be present in suitable amount depending upon thenature of the adsorbent, the amount of expellant gas to be stored in thecharge and the storage pressures desired. The proportions of the drychemical, adsorbent and expellant gas thus may be varied considerably,depending upon the capacity of the extinguisher used and the permissibleloss of expellant gas which can be determined by weighing theextinguisher unit. The following are illustrative examples of chargessuitable for use in a 2 /2 1b. capacity dry chemical extinguisher whichcan be stored prior to use and that can be weighed within A ounce lossof weight to determine whether any expellant gas has been lost duringstorage. The parts are given by weight.

Example 8 Charges :were made for a fire extinguisher containing byweight -90 percent of an alkali metal bicarbonate, 5-15 percent highsurface silica magnesia adsorbent, 0.5 to 1.5 percent halogenatedhydrocarbon and 1.25 to 1.75 percent expellant gas such as nitrogen orcarbon dioxide.

Example 9 Charges were made for a fire extinguisher having 50 to 98percent dry chemical fire-extinguishing powder, 2 to 50 percent highsurface-area silica gel and 2.5 to 10 percent carbon dioxide.

Example 10 Charges were made for a fire extinguisher comprising 50 to 98percent dry chemical fire extinguishing powder, 2 to 35 percent highsurface-area silica gel and 2.5 to 10 percent nitrous oxide.

Example 11 Charges were made for a fire extinguisher comprising 60 topercent dry chemical fire-extinguishing powder, 5 to 35 percent highsurface-area silica gel and 2.5 to 10 percent ethane.

Example 12 Charges were made for a fire extinguisher comprising 60 to 95percent dry chemical fire-extinguishing powder, 5 to 40 percentattapulugus clay and 2.5 to 10 percent of an expellant gas such ascarbon dioxide. Nitrous oxide or ethane may replace the carbon dioxidein this example.

Example 13 Charges were made for a fire extinguisher comprising 50 to 95percent dry chemical fire-extinguishing powder, 5 to 40 percentactivated carbon and 2.5 to 10 percent carbon dioxide. Synthetic zeoliteor activated alumina may replace the activated carbon.

The particle size of the adsorbent is not critical as long as it is of asize that will not obstruct the discharge orifice or otherwise interferewith the discharge of the extinguisher. Usually particles between 100and 200 mesh were used, but successful adsorption characteristics wereeven obtained with A; inch chunks.

'Ihe extinguishers in the above examples will discharge satisfactorilyso long as the pressure of the expelling gas at the start of thedischarge is above -140 p.s.i. We have found that a loss of 20 percent(about seven grams) of the expellant can be detected by weighing theextinguisher on an ordinary scale or balance. We have further found thatafter the loss of 20 percent of the expellant, the pressure remaining inthe extinguisher is still sufficient to provide satisfactory dischargecharacteristics.

For a 2 /2 lb. extinguisher capacity, we have found charges aresatisfactory containing by weight about 50 to about 98 percent drychemical fire-extinguishing powder, about 2 to about 50 percent of ahigh surface-area adsorbent, and from about 2.5 percent to about 10percent of expellant gas. The operations of these components obviouslycan be greatly varied depending upon the capacity of extinguisher inwhich the charge is stored, the proportions being predetermined so thatthe total amount of the gaseous expellant in the container is capable ofexpelling substantially most of the dry chemical stored in the containerand at the same time the stored charge is weighable in the extinguisherso that a weighable amount of the expellant gas, for example, A ounceloss of weight, can permissibly escape or leak from the extinguisherwithout impairment of the fire extinguishing usefulness of theextinguisher. Thus, by the use of a suitable adsorptive agent which canadsorb at least percent by weight of the expellant gas in associationwith the dry chemical in our charge we can, while not raising themaximum pressure above 200 p.s.i. at 70 F., add such a large weight ofexpellant gas that the loss of an easily weighable quantity still leavesthe extinguisher in a state of readiness for use and this isaccomplished while maintaining the dry chemical charge at the maximumamount which can be poured into the extinguisher cavity We claim:

1. In a fire extinguisher, a sealed container having therein a charge,said charge consisting essentially of, by weight, 10 to 50 percent of ahigh surface area adsorbent selected from the group consisting of silicagel, activated carbon, attapulgus clay, synthetic zeolite, activatedalumina, silica-a1umina and silica magnesia, 1.75 to 10% of non-reactiveexpellant gas, said gas being a member selected from the groupconsisting of carbon dioxide, nitrous oxide, ethane, halogenatedhydrocarbon, nitrogen, air, and mixtures thereof, and, the remainder, afreefiowing comminuted fire extinguishing agent, at least 10 percent ofsaid expellant gas being adsorbed on said adsorbent.

2. In a fire extinguisher, a sealed container having therein the chargeof claim 1 wherein said halogenated hydrocarbons are selected from thegroup consisting of dichlorodifluoromethane, monochlorodifiuoromethane,and 1-chlorodifiuoro-2-chlorodifiuoroethane.

3. The fire extinguisher of claim 1, wherein the pressure in said sealedcontainer is below about 200 p.s.i. at 70 F.

4. In a fire extinguisher, a sealed container having therein a charge,said charge consisting essentially of, by weight, 10 to percent of ahigh surface area adsorbent selected from the group consisting of silicagel, activated carbon, attapulgus clay, synthetic zeolite, activatedalumina, silica alumina, and silica magnesia, 2.5 to 10 percent ofnon-reactive expellant gas, said gas being a member selected from thegroup consisting of carbon dioxide, nitrous oxide, ethane, halogenatedhydrocarbons, nitrogen, air, and mixtures thereof, and, the remainder, afree flowing comminuted fire extinguishing agent, at least 10 percent ofsaid expellant gas being adsorbed on said adsorbent.

References Cited in the file of this patent UNITED STATES PATENTS2,605,848 Carter Aug. 5, 1952 2,785,838 Mayer Mar. 19, 1957 2,819,763Boal Jan. 14, 1958 2,881,138 Reiss Apr. 7, 1959 2,901,427 Steppe Aug.25, 1959 UNITED STATES PATENT OFFICE Patent No. 3,055,435

September 25, 1962 William R. Warnock et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4, line 41, for "attapulugus" read attapulgus column 4, line 71,for "operations" read proportions Signed and sealed this 19th day ofMarch 1963.,

(SEAL) Attest:

ESTON G. JOHNSON Attesting Officer DAVID L. LADD Commissioner of PatentsUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,055,435 September 25, 1962 William R. Warnock et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

I Column 4 line 41, for "attapulugus" read attapulgus column 4 line 71,for "operations" read proportions Signed and sealed this 19th day ofMarch 1963.,

(SEAL) Attest:

ESTON G, JOHNSON DAVID L. LADD Attesting Officer a 7 Commissioner ofPatents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0.3,055,435 September 25, 1962 William R. Warnock et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4, line 41, for "attapulugus" read attapulgus column 4 line 71for "operations" read proportions Signed and sealed this 19th day ofMarch 1963..

(SEAL) Attest:

ESTON G. JOHNSON DAVID L. LADD t sting Officer Commissioner of Patents

1. IN A FIRE EXTINGUISHER, A SEALED CONTAINER HAVING THEREIN A CHANGE,SAID CHARGE CONSISTING ESSENTIALLY OF, BY WEIGHT, 10 TO 50 PERCENT OF AHIGH SURFACE AREA ADSORBENT SELECTED FROM THE GROUP CONSITING OF SILICAGEL, ACTIVATED CARBON, ATTAPULGUS CLAY, SYNTHETIC ZOELITE, ACTIVATEDALUMINA, SILICA-ALUMINA AND SILICA MAGNESIA 1.75 TO 10% OF NON-REACTIVEEXPELLANT GAS, SAID GAS BEING A MEMBER SELECTED FROM THE GROUPCONSISTING OF CARBON DIOXIDE NITROUS OXIDE, ETHANE, HALOGENATEDHYDROCARBON, NITROGEN AIR, AND MIXTURES THEREOF, AND, THE REMAINDER, AFREEFLOWING COMMINUTED FIRE EXTINGUISHING AGENT, AT LEAST 10 PERCENT OFSAID EXPELLANT GAS BEING ADSORBED ON SAID ADSORBENT.